A rechargeable secondary battery is generally classified into hard pack batteries and internal batteries. FIG. 1 shows an exploded perspective view of a mobile telecommunication terminal with a conventional internal battery separated from the terminal.
Referring to FIG. 1, the mobile telecommunication terminal with the conventional internal battery comprises a body 100, a battery receiving part 110, a battery pack 120, and a battery cover 130, in which the battery pack 120 is mounted in the body 100 so as to be enclosed by the body 100 and the battery cover 130. For the hard pack battery, the battery pack is provided as a hard pack, and is detachably mounted on a rear side of the body, so that the battery pack is exposed to the outside. On the other hand, the mobile telecommunication terminal as shown in FIG. 1 is provided with the internal battery in which a board having a battery cell and a protective circuit board mounted thereon is received in an external case. In such an internal battery pack, as an approach for holding the battery cell and the protective circuit board, although it has been conventional that the battery cell and the protective circuit board are only received within the external case comprising an upper cover and a lower cover, a manner of filling a low temperature molding resin between the battery cell and the protective circuit board or a manner of coating the battery cell with the low temperature resin and encasing it with a resinous mold has been recently developed for the purpose of reducing the number of components while enhancing the productivity.
Additionally, for the purpose of miniaturization of the battery pack, instead of providing external input and output terminals for connecting the battery pack and external circuits as a terminal block or a lid wire on an outer surface of the battery pack, the external input and output terminals are formed on one side of the protective circuit substrate to be exposed to the outside.
In this case, when manufacturing the battery pack, it is necessary to secure an accurate position of the external input and output terminals relative to the external case or the resinous mold, and for this purpose, the protective circuit substrate must be accurately fixed at a predetermined position to the battery cell when filling the low temperature molding resin. Conventionally, molding is performed in a state wherein the protective circuit substrate is fixed at the predetermined position to the battery cell by inserting a resinous holder between the protective circuit substrate and the battery cell before filling the resin.
However, according to this approach, the resinous holder impedes flow of the resin when filling the resin, thereby causing deterioration of the flow of the resin. As such, when suffering deterioration of the resin during such a molding process, cracks or pin holes are formed inside or outside of the resinous mold of the battery pack, thereby providing insufficient airtightness between the protective circuit substrate and the battery cell which must be sealed by the resinous mold, or providing insufficient strength of the resinous mold, resulting in reduction of the yields.
Meanwhile, although flow of the resin can be prevented from being deteriorated by decreasing a filling speed of the resin or increasing a temperature and a filling pressure of the resin upon filling the resin, there occur other problems, such as reduction in productivity, damage to the battery cell or the protective circuit substrate caused by the heat or the pressure, and the like. Additionally, when using a resin having a lower viscosity, although the deterioration in the flow of the resin can be suppressed, such a material has not been yet provided, which has a low viscosity upon being filled into the mold, while having a sufficient mechanical strength as the resin mold of completed products.
FIGS. 2 to 4 are perspective views of various types of conventional internal battery pack, showing a hard case type internal battery pack, an insert molding type internal battery pack, and a double internal battery pack which adopts aspects of the hard case type battery pack and the insert molding type battery pack.
Various methods for manufacturing the battery pack as mentioned above have been suggested. According to one of the methods, a battery cell holding support and a substrate holding support are inserted into a mold so as to provide a space between the battery cell holding support and the substrate holding support therein, and molding is performed after the space is filled with a molding material within the mold in which a battery cell is supported by the battery cell holding support, and at the same time, a substrate for external input and output terminals is supported by the substrate holding support. According to another method, after encasing an overall protective circuit module (PCM) with a resin in a state of anode and cathode nickel plates being perpendicularly attached thereto, an encased portion of the PCM is joined to a battery cell at both sides thereof by spot welding, in which a bimetal and the nickel plate are perpendicularly attached to a cathode terminal of the battery cell while the other nickel plate is perpendicularly attached to an anode terminal of the battery cell. According to the other method, after a battery cell and a PCM are attached to an injection-molded case, a soft pack is inserted. However, the conventional battery packs have various difficulties in manufacturing.